The present invention constitutes an improvement over the machine tool disclosed in U.S. Pat. No. 3,609,838 to H. Wiest.
In the Wiest patent, a pallet is carried by a rotary gear into rough alignment with successive, peripherally spaced machining locations. The pallet is connected to the gear by means of a "spring pack," wherein a spring urges the pallet and the parts loaded on the pallet vertically upwardly into spaced relation above the gear. At the machining location, the gear is halted, and hydraulically actuated clamping devices pull the pallet downwardly relative to the gear and against the load of the spring pack to fix the pallet to a machine base in accurate alignment for machining.
The spring pack must exert substantial force upwardly to enable the pallet and its load of parts to float above the gear during transport. This spring force must be overcome by the clamping mechanism in order to pull the pallet downwardly into clamped position at each machine station prior to machining. The spring load has proven to be critical in use, and each individual machine tool must be fitted with specific spring packs depending upon the weight of the pallet, the weight and number of the parts to be machined, etc. Additionally, the necessity of overcoming the spring force with the clamping elements reduces the net clamping force securing the pallet in position during machining. It would be desirable from an economic and functional standpoint to eliminate the spring arrangement interposed between the pallet and the carrying gear.
The present invention is also an improvement over the machine tool disclosed in U.S. Pat. No. 4,130,920 issued to Siarto Machine and Tool Company, Inc., the assignee of the present application.
In the latter patent, the machine tool includes an annular gear which is rotatable in a horizontal plane and carries a plurality of pallets between adjacent peripherally arranged machine stations. Hydraulic power mechanisms are provided to raise the gear for transport between adjacent stations and to lower the gear for location at each station successively. The pallets are each carried by the gear and are hydraulically locked by the same hydraulic raising and lowering mechanism into finely adjusted position at each machine station by the use of precisely located telescopically interfitting elements on the gear support table and on the pallets respectively. A means was provided for accommodating final adjusting movement of the pallets relative to the gear at each station yet fixing the pallet relative to the gear during transport thereof.
Further examples in the prior art of machine tools of this type are found in the following U.S. Pat. Nos.: 3,336,823; 3,508,311; 3,479,712; 2,392,169; 2,967,440; and West German Pat. No. 2,531,559 dated July 15, 1975.